In last tonight's episode of Game of Thrones, Arya Stark tailed Littlefinger and found a letter he was hiding in his chambers with a Baratheon seal and a signature by Sansa Stark.

We weren't given a good look at it, but enough words could be seen to identify it as the letter Sansa was forced into sending to her brother Robb back in season 1.

Sansa's letter on Game of Thrones

If you recall, Cersei said that she would believe Sansa's is loyalty on the condition that Sansa write to Robb asking him to bend the knee and swear fealty to Joffrey.

So why would this be of use to Littlefinger?

I need to think on this a little more, but presumably Littlefinger had spotted tension between Arya and Sansa and was hoping to lead Arya to further evidence of her sister being out for herself.

Yes, Sansa initially stood by the evil Joffrey just so she could become queen, but also it was pretty clear that she signed her name under duress, so I'm not sure how useful it can really be in Littlefinger's ongoing manipulations.

There was another early season callback tonight as Gendry returned - you can read more about his history here.

Game of Thrones continues on HBO, Sky Atlantic and through NOWTV on Sunday nights.